Retinopathy of Prematurity (ROP) is one of the leading causes of blindness in newborn infants, with an increased incidence in younger gestational ages. Although numerous risk factors have been identified, the exact pathogenesis of this disease is unknown. Earlier studies suggest that a potent hematogenous photosensitizer-Protoporphyrin IX(PP IX) - found in higher quantities in premature infants may produce ROP by generating toxic reactive oxygen species. These photo-oxidation products are thought to be scavenged by antioxidants such as vitamins A and E, which are known to be low in premature infants. Based on these studies, we hypothesized that high levels of PPIX and low levels of vitamins A and E may increase retinopathy in premature infants. We collected blood levels of PPIX and vitamins A and E in 70 premature infants, gestational age 24-32 weeks with birthweight less than 1200 grams. Blood was collected at birth, 2 and 4 weeks for vitamins A and E. PPIX levels were higher at birth, 1,2,4 and 6 weeks. Blood samples of PPIX have been found to be higher at birth and in lower birthweight infants. Levels of vitamin A and E are initially low, but increase with time. Initial levels are lower in the infants who develop ROP. These findings suggest that high PPIX levels and low vitamin A and E levels seen initially within the first few days of life may be important to the pathogenesis of ROP. Continued studies are necessary, therefore, to evaluate these findings and their association with ROP in babies exposed to varying amounts of light.